Love the stack of books as stool. Careful, though, this is the kind of photo plan that will very likely change course. (imagine books sprawled, toddler not cooperating) A great opportunity to go with it and just see what happens!
Here's a post with an annotated list of books and web sites for studying shadows. Also, this picture gives me an idea for a fun photo op for our unit. The kids could hold up signs to make the words Rosalind Franklin STEM Elementary and or their own names